In Googles' ideal world, it would rank everything according to unbiased relevance.

SEO on the other hand is as much about making your relevance stand out, as is about tipping the scales in your favour through whatever tactics necessary. It's not supposed to be fair, goodness me. :)

Also, you'll never know when Google et all will start to punish sites on certain underhand tactics. The rules change almost daily sometimes, and if you get caught cheating your ranking will be punished; often irrecoverably. It's a game.